Acoustic sensing of underground objects has typically been performed with low frequency waves from widely separated sources. These wavelengths are too long to reliably image underground land mines. High-frequency acoustic or ultrasound waves are difficult to couple into the ground from the air. It is difficult or impossible to get conventional ground contact acoustic sources close to the mine position without risking detonation.
Further, all existing mine detection systems are subject to high rates of false alarms. Ground penetrating radar for example, a common method of mine detection, tends to locate all submerged objects, and does not discriminate sufficiently based on the shape or composition of the located object. In a tactical environment, such an area is likely to contain such objects as battle debris, spent shell casings, and containers from supplies and foodstuffs. Metal detectors, another common detection mechanism, detect all benign and harmful metal objects, and are also blind to plastic and ceramic mines. As typical prior art methods do not adequately report the shape of a submerged object, all objects so found must be suspected as a possible mine. An estimated 300 holes are dug for each live mine actually recovered. Such a low frequency of offending objects tends to promote carelessness, thereby having an overall detrimental effect on the mine detection operation. It would be beneficial to employ a mine detection operation which can provide shape resolution of a submerged object to allow discrimination of benign shapes. It would be further beneficial to employ a mine detection operation which can be performed remotely through a medium which will not cause detonation of a live, submerged mine, and which allows sensing equipment to remain a safe distance from the sensing area.